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How big is the Moon?
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Illustration showing Earth and the Moon side by side against a teal background, highlighting that the Moon is much smaller than the Earth. A label in the top left reads comparing the size of the Moon and Earth. A tennis ball and a basketball are placed side by side on a blue background, illustrating their size difference. A label explains this is like comparing the Moon to Earth if Earth were a basketball and the Moon a tennis ball.
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Illustration showing Earth and the Moon side by side against a teal background, highlighting that the Moon is much smaller than the Earth. A label in the top left reads comparing the size of the Moon and Earth.
Comparing the Size of the Moon and Earth Earth is about four times the size of the Moon

How big is the Moon?

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Britannica Editors
Encyclopaedia Britannica's editors oversee subject areas in which they have extensive knowledge, whether from years of experience gained by working on that content or via study for an advanced degree....
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A tennis ball and a basketball are placed side by side on a blue background, illustrating their size difference. A label explains this is like comparing the Moon to Earth if Earth were a basketball and the Moon a tennis ball.
Comparing the Size of a Tennis Ball and a BasketballIf Earth were the size of a basketball, the Moon would be about the size of a tennis ball.

The Moon is a spherical rocky body with a mean equatorial radius of approximately 1,738 kilometers (1,080 miles) and a diameter of roughly 3,476 kilometers (2,160 miles). In terms of mass, the Moon is relatively massive for a natural satellite, with a mass ratio compared to Earth that is larger than that of most other natural satellites to their respective planets. Its size is substantial enough to exert a strong gravitational influence on Earth, affecting tides and even the length of our days; it is even strong enough that the Moon and Earth orbit a common barycenter located between the two bodies’ cores rather than the Moon orbiting Earth’s center.

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